1. Field of the Invention
The instant disclosure relates to ambient light sensing with stacked photodiode; in particular, to a stacked photodiode for ambient light sensing and a photo sensor having the same.
2. Description of Related Art
Ambient light sensor (ALS) provides outputs that approximate human eye response. It is useful in display brightness management with the purpose of extending mobile battery life and providing optimum viewing experience in diverse indoor and outdoor lighting conditions.
Existing ambient light sensor is implemented in the following ways. Firstly, a single photodiode with coating to emulate human eye response. Secondly, dual diodes with one responsive visible light and infrared (IR) light spectrum, and the other responsive to mainly IR light spectrum, and emulate human eye response based on their difference. However, the earlier has higher manufacturing cost due to additional coating process and it is quite challenging to detect sub-lux lighting condition, while the later has occupied double silicon area and part to part variation is highly depends on how well the dual diodes were matched.